आम लोग: "रेल फैनिंग आती नहीं". RailFans: "रेल फैनिंग जाती नहीं" - Md Asif

The jerks in LHB coaches are due to their CBC couplings. This is not at all related to the type of locomotive hauling the train. Trains like Kaveri express, SBC Raj etc have CBC rakes and are regularly hauled by WAP7 locos and these are notorious for their jerks. ( You can check the Kaveri express forum for long blogs regarding complaints about the jerks and I've personally experienced it in both the trains). Conventional or 3 phaser loco does not have anything to do with the jerks. It's partly luck, and partly the LP's skill that determines whether or not there are jerks with CBC rakes.
Also the statement about jerks in the journeys with conventional...
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locos is absolutely incorrect. It is true that acceleration is done in steps in conventional locos ( called notching), while it is done smoothly in a 3 phaser. However, the LP's skill in handling the notching only determines the acceleration of the loco and it does not cause any jerks. The disadvantage of the notching is that adhesion of the conventional locos is limited and also the TE drops faster than for a 3 phaser. But note that there are absolutely no problems with ride quality with conventional locos, right from the WAG models to the WAP models. Ride quality depends more on the loco's bogie style and the train's rake. And barring the WAP5, all other locos have similar ride quality due to their similar bogie designs.
Popularity of the loco is also a rather subjective opinion. Talking to LP's SCR I've found a strong liking for WAM/P4 style locos. While it is very easy to handle a 3 phaser, note that it requires an intensive technical training to handle 3 phasers ( the internal mechanisms and electronic systems in 3 phasers are extremely complicated compared to conventional locos). Also, tap changers give more control to the LP while a 3 phaser handles most things by itself and some LP's, especially the older generations are more comfortable with having more control on the loco.
Conventional locos are technically way behind the 3 phasers. But in terms of performance, they are no less than the 3 phasers, especially more so in the passenger segment.